Linear and non-linear contrast coding in light-adapted blowfly photoreceptors

The response properties of R1–6 type photoreceptors of the blowfly (Calliphora vicina) were investigated using 1- to 600-ms light steps with contrasts from -1.00 to +1.12 at different adapting backgrounds. To prevent activation of voltage-dependent K⁺-channels, some photoreceptors were treated with ionophoretically injected tetraethylammonium. The linearity and time-course of the photoresponses depended on the adapting background and the duration of the contrast stimulus. At low backgrounds photoresponses were approximately linear regardless of the contrast step duration. However, at higher backgrounds photoreceptors produced, with long contrast steps of opposite polarities, larger and slower hyperpolarizing responses than depolarizing ones, but linear responses with equal time-courses to transient (2ms) contrast changes. The early rising phases of photoresponses were independent of the contrast signal duration, deviated to the same extent from the steady-state potential and steepened as the value of contrast was increased. The photoreceptor contrast gain increased with the background, but its value depended on the duration, the magnitude, and the polarity of the contrast step. Tetraethylammonium linearised the photoreceptor membrane, increased and delayed photoresponses probably by blocking the shunting of the outwardly rectifying potassium channels. These effects did not strongly influence on the photoreceptors' characteristic non-linear contrast dependence on light adaptation.Abbreviations LED light emitting diode - TEA tetraethylammonium ion     

Cross-connections coordinate postural motoneuron activity in the crayfish abdomen

Intracellular recordings and dye injections were used to examine mutual coupling among slow abdominal postural motoneurons in the 4th abdominal ganglion in crayfish (Procambarus clarkii). Intracellular current injection into one motoneuron altered the spike firing rate of some of its synergists. Depending on the polarity of the injected current, the premotor effect on the synergists was excitatory or inhibitory. The magnitude of the effect was intensity dependent. No dye coupling was found among the motoneurons following injection of Lucifer yellow. The morphological basis of the coupling was examined by differential filling of motoneuron pairs, one with horseradish peroxidase and the other with Lucifer yellow. The stained motoneurons were simultaneously visualized under light microscopy to determine the proximity of their differently colored dendrites. It was thus possible to locate the site of the presumed monosynaptic contacts between them. Combined physiological and morphological evidence suggests that these neurons are mutually coupled, forming part of an integrative system for abdominal posture control in crayfish.     

家兔三叉神经终止核对颏舌肌肌电活动的调制作用

本工作在35只氨基甲酸乙酯麻醉、自主呼吸的家兔上观察了刺激三叉神经终止核(NTV)对颏舌肌肌电活动的影响。结果发现,电刺激NTV和NTV内微量注射谷氨酸钠都能使颏舌肌出现明显的易化效应。电刺激NTV背侧与腹侧时,颏舌肌肌电反应的潜伏期分别为5.9±0.7ms和3.0±0.4ms,电刺激舌下神经核时颏舌肌反应的潜伏期为2.2±0.2ms。结果提示三叉神经终止核的兴奋可加强颏舌肌的活动从而减小上呼吸道阻力。     

Effects in vitro of nine fungicides on growth of entomopathogenic fungi

The effects of nine fungicides were evaluated in vitro on the entomopathogenic fungi Beauveria bassiana, Conidiobolus coronatus, C. thromboides, Metarhizium anisopliae, Paecilomyces farinosus, P. fumosoroseus, Scopulariopsis brevicaulis and Verticillium lecanii. The susceptibility of the fungi to the fungicides varied. The dithiocarbamate derivations zineb + copper oxychloride, and mancozeb completely inhibited germination of C. coronatus, C. thromboides, B. bassiana, P. farinosus, M. anisopliae and V. lecanii. The fungicides triadimefon, copper oxychloride, metalaxyl, sulfur, sulfur + nitrothal‐isopropyl and hymexazol exhibited various effects on the fungi. Usually, fungistasis was more pronounced at 15°C than at 25°C and the inhibitory effects were in direct proportion to the dosage of active ingredient (recommended field rate, 10‐fold higher and 10‐fold lower). In a few combinations, fungi partially overcame or even recovered from the initial inhibition of growth which might have resulted from delayed germination. In other cases, inhibition of growth occurred only after a delay and its intensity increased with time. Stimulation of fungal growth when it occurred was rarely permanent. Generally, adverse effects were much greater against the entomophthoraleans C. coronatus and C. thromboides than against the Hyphomycetes. Extrapolation of the results to practice and to the field situation is difficult. Nevertheless, the data presented give an idea of possible side‐effects in nature.     

节律性听觉刺激下的神经振荡同步化及其应用

大脑的感觉、情绪、认知等功能与其神经振荡模式有密切的联系。通过施加节律性刺激可以调控大脑的神经振荡模式,进而影响个体感受、情绪状态和认知功能等。与近年来常见的非侵入性电刺激和磁刺激相比,同样依赖于外部刺激输入的节律性感觉刺激具有成本低、易操作等优点,被认为是一种极具潜力的神经调控手段。本文以节律性听觉刺激为例,系统综述了不同类型的节律性听觉刺激如何影响大脑的神经振荡模式,进而影响相关状态和功能;并通过总结外部节律性听觉刺激对个体感知觉、情绪与认知功能的影响,讨论其生理机制和应用前景。     

偏头痛患者体感刺激下脑电信号的功能连接（英文）

目的 偏头痛是一种复杂的脑功能障碍性疾病,全球范围内患病率为14.4%。功能连接测量两个神经信号之间的统计学相互依赖性,不同的功能连接反映了大脑区域协同工作的不同模式。因此,研究不同脑区的功能连接对于理解偏头痛的病理生理机制具有十分重要的意义。以往基于脑电图对偏头痛患者脑功能连接的分析主要集中在视觉和疼痛刺激。本文尝试研究偏头痛患者在发作间期对体感刺激的皮质反应,以进一步了解偏头痛的神经功能障碍,为偏头痛的预防和治疗提供线索。方法 招募23例无先兆偏头痛患者,10例有先兆偏头痛患者,28名健康对照者。所有受试者均进行详细的基本资料和病史采集,完善量表评估,在正中神经体感刺激下进行脑电图记录。计算68个脑区的相干性作为功能连接,并评估功能连接与临床参数的相关性。结果 在正中神经体感刺激下,无先兆偏头痛和有先兆偏头痛患者的脑电功能连接与对照组相比存在差异,异常的脑电功能连接主要位于感觉辨别、疼痛调节、情绪认知和视觉处理等区域。无先兆偏头痛和有先兆偏头痛患者的大脑皮层对体感刺激可能具有相同的反应方式。偏头痛患者的功能连接异常与临床特征之间存在相关性,可以部分反映偏头痛的严重程度。结论 本研究...     

神经肌肉电刺激下小腿肌肉的电学特性研究

目的 采用电阻抗成像（electrical impedance tomography,EIT）方法研究神经肌肉电刺激（neuromuscular electrical stimulation,NMES）下小腿肌肉的电学特性,旨在将EIT作为一种长期监测方法,从而可视化NMES训练对人类小腿肌肉的训练效果。方法 16名实验对象被随机分配到对照组（control group,CG,n=8）和最佳电压强度的NMES训练组（optimal voltage intensity training group,OG,n=8）。对照组保持正常生活方式并不进行NMES和其他的肌肉训练;NMES训练组中使用商业NMES设备对实验对象右小腿进行23 min的NMES训练,每周3次,为期5周。应用EIT测量在每周一训练开始前的电导率分布。并且采用生物电阻抗分析（bioelectrical impedance analysis,BIA）方法测量右腿细胞外含水量与身体总含水量的比率（ECW/TBW） βrl,及身体总含水量（TBW）τ。为了量化NMES在肌肉训练过程中的作用,使用配对样本t检验分析EIT重建图像的...     

脑部磁刺激场的理论模型

作为脑部磁刺激研究的一项基础工作,建立了刺激磁场中的球形头模型、对方形线圈在其内产生的时变磁场和感应电场进行了理论研究.导出(?).(?).(?)的解析表达式,分析了场的特性和刺激强度的分布规律.为进一步探索时变磁场对人脑的最佳刺激方式和作用机理提供了初步的理论基础.     

Light (Blt), a Mutation That Causes Melanocyte Death,Affects Stria Vascularis Function in the Mouse Inner Ear

The Light mutation (B^lt) is a dominant allele of the b-locus on mouse chromosome 4 which causes progressive dilution of coat colour. Melanocytes within the hair follicles of mutant mice develop normally but later degenerate, due to the accumulation of a toxic product, so that the hair becomes lighter with age. Previous studies on W-locus spotting mutants, from which melanocytes are absent, have shown that melanocytes in the stria vascularis of the inner ear are essential for the development and/or maintenance of the endocochlear potential (EP) which is normally around 100 mV. In this study, physiological recordings from the ears of Light mutants were correlated with strial ultrastructure. EPs recorded from all b/b controls and young homozygous and heterozygous mutants (20–22 days old) were normal (77 to 113 mV), but were reduced (19 to 59 mV) in about 30% of ears from older mutants (B^lt/B^lt and B^lt/b). Strial function therefore appears to develop normally but later degenerates in some mutants. This suggests that strial melanocytes are affected by the Light allele and that the continued presence of melanocytes is necessary for strial function. There was no obvious association between the recorded EP value and the ultrastructural appearance of the stria. No structural abnormalities of the stria were noted in control or mutant mice aged 20 days to 4 months including those which had a reduced EP. Strial atrophy was common in old controls and mutants (1–2 years), and appeared to be an age-related process rather than an effect of the Light mutation. Similarly, pigment build-up was common in all strial cells of old mice. However, the accumulations of lipofuscin-like pigment were much larger and more abundant in aged brown non-agouti mice than those observed in old agouti mice, which suggests that this age-related process also has a genetic component.     

Melanization Stimulating Activity in the Skin of the Gilthead Porgy,Sparus auratus

The presence of a melanization-stimulating factor (MSF) was discovered in dorsal and/or ventral skin of Sparus auratus. Skin from this marine species was used to condition Steinberg's balanced salt solution (BSS), which was subsequently tested with the neural tube assay. BBS conditioned by dorsal and/or ventral skin of S. auratus at 25% and 50% concentrations had a profound stimulatory effect on the percentage of melanization of neural crest cells throughout the 3day assay period. In some cases 90% melanization occurred within the first 24 hr. Such stimulated cells showed a doubling of the number of dendrites per cell. assess the effects of MSF on other indices of melanization, dorsal and/or ventral skin was used to condition MEM used in the culture of B16-F10 murine melanoma cells. During the first 24 hr, B16-F10 murine melanoma cells responded to conditioned media by demonstrating a considerable increase in activities of tyrosine hydroxylase, dopa oxidase, and dopachrome tautomerase, but no effect was observed on melanin content. In contrast, melanin content increased after 48 hr of incubation, whereas the enzymatic activities were inhibited during this period. It seems that MSF activity, expressed in several ways, may be present generally among marine species.